The microstructure and performance of welded joints is an important basis for judging the quality of joints. With reasonable welding parameters,joints with excellent microstructure and performance can be obtained. In this paper,a automatic downward filling cosmetic welding procedure with self-shielded flux-cored wire for X70 steel pipe φ1 016 mm×17.5 mm is studied.By analyzing the arc trajectory in the welding process,according to the four parameters of heat input q,1, and q,2,arc edge straight distance H,1, and welding blind zone length H,2,the welding parameters are set and three test schemes are developed. The welding procedure is evaluated by analyzing the microstructure of each area of the welded joint with SEM;the mechanical properties of the welded joint are analyzed through a series of mechanical performance tests such as tensile,three-sided grooved hammer break,side bending test and low temperature impact test. The results show that the appearance of weld can be well controlled by adjusting the heat input q,the arc edge straight distance H,1, and the welding blind zone length H,2,. The matching of the welding parameters set up in the No.2 test case is more reasonable,and is suitable for this set of automatic welding equipment for the long-distance pipeline. By optimizing on the basis of this set of welding parameters,more optimal sets of welding parameter matching can be obtained and the universality and adaptability of this system and equipment are improved.